Research On Low-Toxic Solvent And Topological Insulator Electrode Based Perovskite Solar Cells

In recent years,due to the high power conversion efficiency(PCE),simple fabrication process and low cost,perovskite solar cells(PSCs)have attracted a lot of attention from researchers.Up to now,the highest PCE of PSCs has exceeded 25%.It means that PSCs have become strong competitor in the photovoltaic field,comparable to the widely used silicon solar cells,mature cadmium telluride and copper indium gallium selenide based thin film solar cells.Among them,the inverted planar PSCs can be completed at a lower temperature throughout the preparation process,which not only simplifies the preparation process,compresses the device fabrication cost,but also can be applied to the preparation of flexible solar cells.Therefore,they have gradually attracted wide interest from researchers.Although the inverted planar flexible PSCs have made a breakthrough,the highest PCE in the laboratory has reached 19.0%.They have reached the level of commercial application,but they still face many challenges on the way to the practical commercial application,such as continuing to improve the PCE,improving the stability and improving the problem of toxic pollution,et al.In this paper,we take the NiO_x-based inverted planar PSCs as the research core.By introducing a new low-toxic anti-solvent and further introducing a low-toxic solvent system,both of the problem of toxic pollution and the efficiency of the PSCs have been improved.On this basis,highly efficient flexible PSCs were fabricated.The main contents were as follow:Firstly,a new low-toxic anti-solvent-tetraethyl orthosilicate(TEOS)was developed to replace the traditional toxic toluene(TL)and chlorobenzene(CB)for the preparation of MAPb I₃ perovskite film,and the inverted planar PSCs were fabricated.This method alleviated the problem of toxic pollution in the preparation process of PSCs.It was found that the perovskite film prepared by TEOS has better quality and the grain size was larger,compared with those prepared by TL or CB,which was beneficial to the performance of PSCs.As a result,the champion PCE reached 17.02%.At the same time,due to the difference in physical properties of different anti-solvents,a pure intermediate phase rather than a mixture of intermediate phase and perovskite phase was obtained after using TEOS as an anti-solvent,which widened the anti-solvent operation window and helped to improve the repeatability of device preparation.Secondly,a low-toxic solvent system-tetraethyl orthocarbonate-anisole(TEOC-AS)was developed to replace the toxic CB-CB solvent system for the preparation of MAPb I₃perovskite film and PCBM electron transport layer,and inverted planar PSCs were fabricated.This strategy alleviated the problem of toxic pollution in the fabrication process of PSCs.At the same time,the PSCs processed by the low-toxic solvent system were demonstrated to have higher efficiencies than the CB counterparts,achieving a champion efficiency of 18.15%.This result was benefited from the improved film quality of perovskite and PCBM electron transport layer.Lastly,based on the previous works,a new type of counter electrode material,Bi₂Te₃,was developed to replace the traditional metal Ag electrode and it was successfully applied to the preparation of low-toxic flexible PSCs.It indicated that,the carrier transport rate from the perovskite layer to the Bi₂Te₃ counter electrode was accelerated,which effectively improved the efficiency of PSCs,and the highest value reached 18.16%.In addition,the Bi₂Te₃ PSC exhibited superior mechanical durability,retaining over 95%of its original PCE even after 1000 bending cycles at a curvature radius of 4 mm,significantly outperforming the reference Ag PSC.This excellent mechanical flexibility was on par with the best-reported results.Furthermore,the air,thermal and light stability of the flexible PSCs were significantly improved when the Ag electrode was substituted with the Bi₂Te₃ electrode.The PCE of the Bi₂Te₃ device showed little loss for up to 1000hours in air with constant temperature and humidity controlled,remained about 90%of its initial value after a continuous heat treatment at 85?for 1000 hours in N₂ and retained about 85%of its initial value after a continuous light illumination for 1000 hours in controlled air condition.